Disposable cylindrical cutter

ABSTRACT

A single use bone cutter comprised of two concentric cylinders and a series of insert blades or cutter disc is described. The cutter blades or cutter disc is preferably positioned at the distal end of the cutter. The bone cutter also comprises a guide rod that aids in the line of sight when using the cutter device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 61/346,976, filed May 21, 2010.

FIELD OF THE INVENTION

The present invention relates to the art of orthopedic cutting tools,and more particularly, to a disposable cutter used for shaping andpreparing the femoral bone for implant insertion.

PRIOR ART

Cutting tools used in orthopedic procedures are designed to cut bone andassociated tissue matter. Specifically, cutters of the present inventionare designed to cut and shape the end of a long bone such as a femur orhumerus. Typically, the end of the long bone is cut and shaped forinsertion of an implant. As such, these cutters are required to besterile and sharp. Using a dull cutter generates heat that typicallyleads to tissue necrosis and results in undesireable patient outcomes. Anon-sterile cutter blade typically results in an infected and damagedbone that may lead to other problems for the patient.

Depicted in FIGS. 1 and 1A are images of a prior art bone cutter 10designed to cut and shape the femoral head 12 of the femur 14. As shownin the figures, the prior art cutter 10 is similar to that of a “holesaw” drill. These prior devices 10 generally comprise a hollow cylinderin which a series of cutting teeth slots 16 are formed within thecylinder wall thickness 18. However, these prior devices 10 do notremove all the bone 14 required to properly fit an implant. Therefore,additional procedures are required to remove this extra bone material 22and smooth the surface of the bone end 24.

As shown in FIG. 1A, the prior cutter device 10 imparts a channel 20within the end 24 of the bone 14. This channel 20 and associated bonematerial 22 proximate the channel 20, must be removed to properly fitthe implant (not shown) on the end 24 of the bone 14. Typically, handtools such as rongeurs are used to remove this extra bone material 22.

Such a bone removal procedure makes it difficult to properly fit animplant over the end 24 of the bone 14. The extra bone material 22 mustbe intricately removed to produce a smooth surface and ensure that thebone 14 is shaped to meet the exacting dimensions of the implant. If theimplant is not properly fit over the end 24 of the bone 14, undesirableimplant wear or improper implant operation could result.

In addition to the inefficient bone removal limitations, traditionalbone cutters are typically reused multiple times. That is because oftheir high cost. Such multiple reuses require that the cutter be cleanedand sterilized before each use. Furthermore, over time, as these cuttersare used and reused, they become dull, thus requiring resharpening.Therefore the blades of the cutter are required to be resharpened,cleaned and sterilized. However, these resharpening and sterilizationprocesses add additional costs and increase the possibility ofinfection. In addition, resharpening tends to deform the dimensions ofthe cutter. These dimensional changes could adversly impact the optimalfit and function of the implant. Furthermore, there is a high likelihoodthat the cleaning and sterilization process may not remove all possibleinfection agents such as bacteria, machining lubricants, and the like.

Accordingly, the present invention provides a cost effective single usebone cutter with a novel blade and assembly design that improves cuttingefficiency. The enhanced bone cutting and shaping efficiencies of thepresent invention ensure proper implant fit and reduced implant wear. Inaddition, the improved bone cutting efficiencies afforded by the presentinvention, decrease procedural time and minimize patient trauma.Furthermore, the bone cutter of the present invention ensures propercutter sharpness and cleanliness that promotes optimal patient outcomes.

SUMMARY OF THE INVENTION

The present invention provides a disposable bone cutter devicecomprising a cutter assembly and guide rod for orthopedic surgicalapplications. Specifically, the cutter device of the present inventionis designed to re-shape the head of a femur for joint revisionsurgeries.

The cutter assembly comprises a disposable housing and a series ofinsert blades or a cutter disc arranged in circumferential manner withinthe assembly. The series of insert blades or cutter disc are preferablysecured in the cutter assembly through an interference fit at a distalbase portion of the cutter assembly.

The housing comprises two cylinders that are joined together at a distalportion of the housing. In a preferred embodiment, a first cylinder ispositioned such that its inner diameter circumferentially surrounds theouter diameter of a second cylinder. Both the first and second cylindersare positioned such that they share a common central longitudinal axis.A series of radial connectors join the two cylinders together along thedistal base portion of the assembly. In a preferred embodiment, theseconnectors may take the form of a bar or rod or alternatively be formedinto a blade enclosure designed to secure and house the individualinsert cutter blades.

Furthermore, it is preferred that the distal base portion of thecentrally located second cylinder is recessed or offset from the distalbase of the first cylinder. This recess establishes an offset rim formedby the wall thickness of the first cylinder. The depth of the offset rimis determined by the gap between the distal base plane of the firstcylilnder and the distal base plane of the second cylinder. The offsetrim provides a barrier that prevents unintentional damage to nearby boneand/or tissue resulting from contact with the cutting surface of theinsert blades or cutting disc.

Located at the proximal end portion of the assembly, within the interiorof the inner diameter of the centrally located second cylinder, is aboss. The boss comprises a central throughbore that is positioned suchthat the throughbore is coaxial with the common longitudinal axis. Thethroughbore of the boss provides an alignment aid to the axis of thedesired cut.

Another feature of the boss is that it acts as a “stop” to preventovercutting of the bone. As will be explained in greater detail, thedistal end of the boss comes into contact with the end of the bone thuspreventing further advancement of the cutter. As such, the position ofthe boss preferably determines the depth of cut into the bone andprevents unintentional overcutting of the end of the bone.

The boss is joined within the interior of the second cylinder through aseries of rods which radially extend between the exterior wall surfaceof the boss and an interior wall surface of the inner diameter of thesecond cylinder. In addition, these rods serve as an interfacing featureby which the cylindrical cutter attaches to a handle or a motor thatrotates the cutter in a clockwide or counterclockwise direction. In apreferred embodiment, the housing can be produced as a single componentusing an injection molding process.

The insert blades are universal and can be manufactured to a minimalsize to accommodate all sizes of the cutter. In a preferred embodiment,the series of individual cutter blades are secured within theirrespective blade enclosures. These blades are preferably of an “L” shapeand are designed to provide a cutting edge that extends into theinterior of the centrally located second cylinder.

The cutter insert blades preferrably include a slot, residing within thesurface that extends along the width of the blade. The slot is designedto interface with a post positioned within the blade enclosure. Theinteraction between the post and slot secures the insert bladetherewithin.

In this embodiment, the cylindrical cutter is assembled by pressing theinsert blades into the blade enclosures of the assembly. The insertblades are designed such that they snap into the blade enclosure. Thislow cost production process, along with the economical production of thecomponent parts, avoids the need for expensive machining and grindingoperations that are common with the prior art.

In an alternate embodiment, a cutter disc having a plurality of cuttingteeth openings, resides within the distal base portion of the assembly.In a preferred embodiment, the cutting disc comprises an outer diameter,an inner diameter, and a planar surface therebetween. The plurality ofcutting teeth are positioned at spaced intervals throughout the planarsurface.

In operation, the femoral head is first shaped to accept a replacementshell of an implant utilizing the present invention. The shaping of thefemoral head is accomplished by first establishing an axis of cut on thefemoral head. This axis is established by drilling a guide hole into thefemoral head and placing a guide rod into the bone. This guide rodserves to align the axis of the cylindrical cutter to the axis of theintended cut. The cutter of the present invention is then attached tothe handle-driver assembly and positioned over the guide rod by means ofthe hollow boss within the cylindrical cutter. The powered driverprovides a means of rotating the cylindrical cutter and advancing thecutter against the femoral head.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art bone cutter and bone.

FIG. 1A is a cross-sectional view of the prior art bone cutter and boneshown in FIG. 1.

FIG. 2 is a perspective view of the cutter housing of the presentinvention.

FIG. 3 is an alternate perspective view of the cutter housing of thepresent invention.

FIG. 4 is a cross-sectional view of the cutter housing of the presentinvention.

FIG. 5 is a perspective view of an embodiment of a cutter blade of thepresent invention.

FIG. 6 is a side view of the embodiment of the cutter blade shown inFIG. 5.

FIG. 7 is a perspective view of an alternate embodiment of a cutterblade of the present invention.

FIG. 8 is a perspective view illustrating an assembly step of thepresent invention.

FIG. 8A is a perspective view illustrating a preferred embodiment of anassembled bone cutter assembly of the present invention.

FIG. 9 is a perspective view of a preferred embodiment of a cutter discof the present invention.

FIG. 10 is a perspective view of the cutter disc and an alternativecutter housing embodiment of the present invention.

FIG. 10A is a perspective view of an assembled alternate embodiment ofthe bone cutter assembly of the present invention shown in FIG. 10.

FIG. 10B is a cross-sectional view of an assembled alternate embodimentof the bone cutter assembly of the present invention shown in FIG. 10.

FIG. 11 is a cross-sectional view of an embodiment of the bone cutter ofthe present invention being used to shape the end of a bone.

FIG. 11A is a cross-sectional view illustrating the shaped end of a boneafter using the bone cutter of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now turning to the figures, FIGS. 2-11A illustrate embodiments of a bonecutter 30 of the present invention. In a preferred embodiment, the bonecutter 30 comprises a cutter housing 32, cutter blades 34 or cutter disc78, and a guide rod 36 (FIGS. 11, 11A).

As shown in FIGS. 2-4, 8, 8A, and 10-11A, the cutter housing 32preferably comprises two cylinders, a first cylinder 38 and a secondcylinder 40 that are joined therebetween. In a preferred embodiment, thefirst cylinder 38 comprises a first cylinder inner diameter 42, a firstcylinder outer diameter 44, and a first cylinder wall thickness 46therebetween. The second cylinder 40 comprises a second cylinder innerdiameter 48, a second cylinder outer diameter 50, and a second cylinderwall thickness 52 therebetween.

In addition, the first cylinder 38 comprises a first cylinder height 54extending from a first cylinder distal base portion 56 to a firstcylinder proximal end portion 58. In a preferred embodiment, the distalbase portion 56 of the first cylinder 38 is co-planar with an imaginaryfirst cylinder base plane B-B (FIG. 4). This imaginary base plane B-Bpreferably extends outwardly from the outer diameter 44 of the firstcylinder base portion 56.

The second cylinder 40 comprises a second cylinder height 60 extendingfrom a second cylinder distal base portion 62 to a second cylinderproximal end portion 64. In a preferred embodiment, the distal baseportion. 62 of the second cylinder 40 is co-planar with an imaginarysecond cylinder base plane C-C (FIG. 4). This imaginary base plane C-Cpreferably extends outwardly from the outer diameter 50 of the secondcylinder base portion 62.

In a preferred embodiment, the first and second cylinders 38, 40 arejoined such that the outer diameter 50 of the second cylinder 40 ispositioned within the inner diameter 42 of the first cylinder 38. Thefirst and second cylinders 38, 40 are further positioned such that theyare co-axial to a common central longitudinal axis A-A as shown in FIGS.2-4, 8, 8A, and 10-11A.

In a preferred embodiment, the outer diameter 44 of the first cylinder38 ranges from about 5 cm to about 10 cm, the inner diameter 42 of thefirst cylinder 38 ranges from about 4.5 cm to about 9.95 cm and theheight 54 of the first cylinder 38 ranges from about 1 cm to about 4 cm.The wall thickness 46 of the first cylinder 38 preferably ranges fromabout 0.05 cm to about 0.5 cm.

In a preferred embodiment, illustrated in FIGS. 2-4, 8, 8A, and 10-11A,the height 60 of the centrally located second cylinder 40 is greaterthan that of the height 54 of the first cylinder 38. Furthermore, theheight 60 of the centrally located second cylinder 40 ranges from about5 cm to about 10 cm. The outer diameter 50 of the second cylinder 40ranges from about 3 cm to about 6 cm and the inner diameter 48 of thesecond cylinder 40 ranges from about 2 cm to about 6 cm. The wallthickness 52 of the second cylinder 40 ranges from about 0.05 cm toabout 0.5 cm.

The two cylinders 38, 40 are joined together by a connector 66 thatinterfaces between the two cylinders 38, 40 at a distal end portion 67of the housing 32 as shown in FIG. 10. The connector 66 can be of manynon-limiting forms such as a bar, a rod, a rectangle or a sphere suchthat one surface interfaces with the interior wall surface 68 of theinner diameter 42 of the first cylinder 38 and an opposite surfaceinterfaces with the exterior wall surface 70 of the outer diameter 50 ofthe second cylinder 40. In a preferred embodiment, a plurality of two ormore connectors 66, radially extend between the inner and outerdiameters 42, 50 of the first and second cylinders 38, 40, respectively,and join them therebetween as shown in FIG. 10.

In a preferred embodiment, the connector 66 can be designed as a bladeenclosure 72 such that individual insert blades 34 (FIGS. 2-3, and 8-8A)are disposed therewithin. This preferred blade enclosure 72 embodiment,will be discussed in more detail.

As shown in the embodiments illustrated in FIGS. 3-4, 8-8A, and 10-10A,the housing 32 is preferably constructed such that an offset rim 74 isformed by a portion of the wall thickness 46 of the first cylinder 38.The depth 76 of the offset rim 74 is defined by the distance between thefirst and second imaginary distal base planes B-B, C-C as shown in thecross sectional view of FIG. 4. In a preferred embodiment, the offsetrim 74 preferably has a depth 76 that ranges from about 0.01 cm to about0.05 cm. The offset rim 74 preferably extends around the perimeter ofthe first cylinder 38 at the distal base portion 56. The thickness ofthe offset rim 74 is defined by the wall thickness 46 of the outer firstcylinder 38.

The offset rim 74 is designed to prevent the cutter blades 34 or cutterdisc 78 (FIG. 9) from inadvertently damaging nearby bone or tissue,particularly preventing a proximal bone or tissue from being cut ornicked. However, it is contemplated that the housing 32 could beconstructed such that the first and second imaginary planes B-B, C-C arecoplanar, therefore constructing a housing 32 without an offset rim 74.

It is preferred that both the first and second cylinders 38, 40 have ahollow interior 80, 82 within their respective inner diameters 42, 48.Such a hollow interior 80, 82 allows for efficient removal of bonedebris as the debris can freely flow through the cutter assembly 84(FIGS. 8, 8A). It is also contemplated that such a housing 32, could beconstructed with a cylinder having a solid or partially solid interior.

In a preferred embodiment shown in FIGS. 2, 4, 8A, and 11-11A, thecutter housing 32 has a boss 86 that is positioned within the innerdiameter 48 of the second cylinder 40. More specifically, the boss 86 iscentrally positioned within the inner diameter 48 of the second cylinder40. In a preferred embodiment, the boss 86 comprises a throughbore 88.The boss 86 is preferably further positioned within the inner diameter48 of the second cylinder 40 such that the throughbore 88 is co-axiallyaligned with the central axis A-A of the housing 32 as shown in FIGS. 2,4, 8A, and 11-11A.

In a preferred embodiment, illustrated in FIG. 4, the boss 86 isconstructed with a distal planar edge 90. This distal planar edge 90 isdesigned to act as a “stop” to prevent further advancement of the cutter30 into the end 24 of the bone 14. The boss 86 is preferably positionedwith the interior 82 of the second cylinder 40 such that a cut depth 92is defined between the distal planar edge 90 of the boss 86 and theimaginary second cylinder base plane C-C. It is contemplated that thisdistal planar edge 90 can be positioned anywhere within the interior 82of the centrally located second cylinder 40 to establish an optimal cutdepth 92 for a particular implant (not shown). In a preferred embodimentthe cut depth 92 ranges from about 2 cm to about 10 cm.

A plurality of bars 94 secure the boss 86 within the inner diameter 48of the centrally located second cylinder 40. A plurality of bars 94,having a length 96 from about 4 cm to about 8 cm and a thickness 98 fromabout 0.5 cm to about 1 cm, fluidly extend from the interior wallsurface 68 of the inner diameter 48 of the first cylinder 38 to theexterior wall surface 70 of the outer diameter 50 of the second cylinder40 within the proximal portion 64 of the housing 32. It is preferredthat a plurality of at least two bars 94, connect the boss 86 within theinterior 82 of the second cylinder 40.

It is preferred that the housing 32 be composed of a biocompatiblematerial. In a preferred embodiment, the cutter housing 32 is composedof a biocompatible thermoplastic such as, but not limited to,Acrylonitrile Butadiene Styrene (ABS), Polyarylamide (PAA), orPolyetheretherketone (PEEK).

Furthermore it is preferred that the series of cutter blades 34 arepositioned in a radial fashion about the outer diameter 50 of the secondcylinder 40 as illustrated in FIGS. 8 and 8A. More specifically, thesecutter insert blades 34 are positioned between the exterior surface 70of the outer diameter 50 of the second cylinder 40 and the interiorsurface 68 of the inner diameter 42 of the first cylinder 38 at thedistal base portion 56 of the housing 32.

Preferred embodiments of the cutter insert blade 34, 130 are shown inFIGS. 5-7. As illustrated, insert blades 34, 130 comprise a bladeproximal portion 100 and a blade distal portion 102. The widths 104, 106of the proximal and distal portions 100, 102 are not necessarily equal.In a preferred embodiment, the width 106 of the distal portion 102 isgreater than the width 104 of the proximal portion 100. An insert bladecutting surface 108 preferably extends along the distal width 106 of theinsert blade 34, 130. In a preferred embodiment, when inserted into thebone cutter housing 32, the plurality of these blade cutting surfaces108 align to form an imaginary blade cutting surface plane D-D (FIG. 4).It is further preferred that this imaginary blade cutting surface planeD-D reside between the imaginary first and second cylinder planes B-B,C-C.

As shown in FIGS. 5, 7 and 8A, the distal width 106 of the insert blade34, 130 is greater than the proximal width 104 of the blade 34, 130.This extra “width portion” of the insert cutter blade 34, 130 is definedas the blade extension portion 110. The blade extension portion 110 isdesigned such that when the cutter blade 34, 130 is inserted into thehousing 32, the extension portion 110 protrudes past the inner diameter48 of the second cylinder 40 towards the interior 82 of the secondcylinder 40.

In addition, the blade extension portion 110 acts as a “free end”. This“free end” extension is designed to cut into the head 12 of the bone 14.As such, this “free end” extension 110 defines a new diameter 112 of thebone head 12 as illustrated in FIG. 11A. If such an extension 110 werenot present, the interior wall 69 of the second cylinder 40 wouldprevent cutting of the bone 14. In a preferred embodiment, the bladeextension 110 has a width from about 0.05 cm to about 0.10 cm.

As illustrated in FIGS. 5 and 6, a groove 114 is preferably formedwithin the surface 116 of the distal end portion 102 of the insert blade34. In a preferred embodiment, the groove 114 has a “V” shape. Thegroove 114 is designed to establish a rake angle θ of the insert blade34. The rake angle θ is defined as the intersection between the distalsurface 120 of the “V” cut out portion 114 and a perpendicular line E-Eto the cutting edge surface 108 as shown in FIG. 6. It is preferred thatrake angle θ range from about 4° to about 30°.

A relief angle Ø, as illustrated in FIG. 6, is formed between theintersection of the distal end surface 124 of the blade 34 and a tangentline F-F to the blade cutting edge 108. It is preferred that the reliefangle Ø range from about 4° to about 20°.

Each cutter blade 34, 130 is preferably positioned within the cutterblade enclosure 72 as shown in FIGS. 8 and 8A. In a preferredembodiment, the insert blade 34, 130 is positioned in the housing 32such that the proximal end portion 104 of the insert blade 34, 130resides inside the blade enclosure 72 and the cutting surface 108 of theinsert blade 34, 130 lies outside the blade enclosure 72. Furthermore,it is preferred that the cutting surface 108 of the insert blade 34 liesparallel to an imaginary cutting plane D-D as shown in FIG. 4. As shownin FIG. 4, the imaginary cutting plane D-D lies between the firstcylinder imaginary plane B-B and the second cylinder imaginary planeC-C. The blade extension 110 preferably is positioned towards thecentral axis A-A of the assembly 84.

In a preferred embodiment shown in FIGS. 2 and 3, each cutter bladeenclosure 72 has a post 126 therewithin. The post 126 is preferablydesigned to snap-fit into a slot 128 within the proximal end portion 100of the cutter blade 34 (FIGS. 5 and 6). Once the post 126 snaps into theslot 128, the insert blade 34 is locked within the cutter bladeenclosure 72.

In an alternative embodiment, as shown in FIG. 7, the insert blade 130can be designed without a groove 114 and slot 128. In this embodiment,the cutting edge 108 is formed at the intersection of the side bladesurface 116 and the distal end surface 124. It is preferred that aportion of the surface 116 at the proximal end portion 100 of the insertblade 130 has a roughened finish 132. This roughened surface finishportion 132 provides for a more secure fit when positioned within theblade enclosure 72.

In a preferred embodiment, insert blades 34, 130 are secured within theblade enclosure 72 with an induction bonding process. Alternatively, theinsert blade 34, 130 can be secured by an alternate means not limited toadhesives, overmolding, press fitting, induction bonding, and the like.

In an alternate embodiment, the cutting disc 78 is positioned at thedistal end portion 67 of the housing 32. The cutting disc 78 embodimentprovides an additional means of bone removal which is illustrated inFIGS. 9-10A. An embodiment of this alternate cutter assembly 146 isshown in FIG. 10A. The assembly 146 of this embodiment comprises thehousing 32 and the cutter disc 78.

The cutting disc 78 preferably comprises an outer disc diameter 134, aninner disc diameter 136 and a planar surface 138 therebetween. Thecutting disc 78 is positioned between the wall thickness 46 of the firstcylinder 38 and the wall thickness 52 of the second cylinder 40 at thedistal end portion 67. More specifically, it is preferred that thecutting disc 78 be placed between the inner diameter 42 of the firstcylinder 38 and the inner diameter 48 of the second cylinder 40 suchthat the planar surface 138 of the cutting disc 78 is parallel to thefirst and second cylinder imaginary planes B-B, C-C (FIG. 10B).

Positioned throughout the surface 138 of the disc 78 are a series ofopenings 140. These openings 140 are preferably positioned throughoutthe surface 138 of the disc 78 in a helical pattern. Protruding from theopening 140 is a cutting tooth 142. The cutting teeth 142 are designedsuch that a cutting surface 144 is positioned outwardly from the planarsurface 138 of the disc 78. Alternately, the cutting surface 144 mayprotrude inwardly from the surface 138 of the disc 78. In a preferredembodiment, these cutting surfaces 144 of the cutting teeth 142 align toform an imaginary cutting disc plane G-G. This imaginary plane G-Gpreferably resides between the first and second imaginary cylinderplanes B-B, C-C (FIG. 10B).

It is preferred that the cutter insert blades 34, 130 and the cuttingdisc 78 are composed of a biocompatible metal. In a preferredembodiment, such biocompatible metals include, but are not limited to,stainless steel, MP35N, titanium, and combinations thereof. It is mostpreferred that cutter blades 34, 130 and the cutting disc 78 arecomposed of a 300 series stainless steel.

In a preferred embodiment, the cutter housing 32 is first molded from abiocompatible polymer as previously mentioned. After the housing 32 hasbeen molded, the cutter blades 34, 130 or cutter disc 78 are theninserted in the distal base portion 67 of the housing 32. As previouslymentioned, an induction bonding process is preferably used to secure thecutter blades 34, 130 or cutter disc 78 to the molded assembly 84, 146.Alternatively, adhesives, overmolding, press fitting, and the like mayalso be used.

In this preferred bonding embodiment, electromagnetic current is used toheat the blades 34, 130 or blade disc 78. Heat generated from thecurrent, melts the surrounding assembly polymer material, causing thematerial to flow and engage the cutter blades 34, 130 or disc 78. It iswell known that alternative processes such as cross pinned engagements,direct insert molding, or ultrasonic insertion may also be used tostrengthen the connection or act as a primary means to join the bonecutter 30 of the present invention.

FIGS. 11 and 11A illustrate the use of the bone cutter 30 of the presentinvention. Initially, a guide-hole 148 is drilled into the end 24 of abone 14. The guide rod 36 is placed into the guide-hole 148 and thecutter assembly 84, 146 is placed over the rod 36 as shown. In apreferred embodiment, the guide rod 36 is preferably positioned throughthe central axis A-A of the bone cutter 30.

Once in place over the end 24 of the bone 14, the cutter 30 is rotatedin either a clockwise or counterclockwise direction. This rotationalmovement of the cutter 30, removes bone material from the end 24 of thebone 14 with a smooth surface finish with a bone diameter 112 suitablysized for insertion of an implant (not shown). Once the bone head 12 isproperly shaped, the cutter 30 and guide rod 36 are removed. An implant(not shown) is then positioned over the end 24 of the bone 14.

Now, it is therefore apparent that the present invention has manyfeatures and benefits among which are promoting proper implant fit,decreased procedural times and minimized patient trauma. Whileembodiments of the present invention have been described in detail, thatis for the purpose of illustration, not limitation.

What is claimed is:
 1. A bone cutter, comprising: a) a first sidewallcomprising a first inner surface providing a first lumen extending alonga longitudinal axis from a first sidewall proximal portion to a firstsidewall distal portion having a first sidewall distal end residingalong a first imaginary plane; b) a second sidewall comprising a secondinner surface spaced from a second outer surface by a second sidewallthickness to thereby provide a second lumen extending along thelongitudinal axis from a second sidewall proximal portion to a secondsidewall distal Portion having a second sidewall distal end residingalong a second imaginary plane, c) wherein the first and secondsidewalls are fixedly joined to each other in a co-axial relationshipwith the outer surface of the second sidewall being radially inside theinner surface of the first sidewall with the second imaginary planebeing more proximal along the longitudinal axis than the first imaginaryplane to thereby provide an offset; d) a cutter disc comprising a discwall extending from an annular outer disc edge to an inner disc edgesurrounding a disc opening, the cutter disc having a disc thicknessextending from a proximal disc face to a distal disc face, wherein theproximal cutter disc face is supported on the second sidewall distal endwith the annular outer disc edge in contact with the inner surface ofthe first sidewall distal portion; and e) a plurality of cutting teethon the cutter disc, each cutting tooth having a tooth opening extendingthrough the disc wall and a tooth cutting surface extending away fromthe distal disc face towards the first imaginary plane, wherein eachtooth opening provides open communication at least into the first lumenbetween the first and second sidewalls.
 2. The bone cutter of claim 1wherein an inner diameter of the second sidewall is greater than aninner diameter at the inner disc edge of the cutter disc.
 3. The bonecutter of claim 1 wherein a distal end of each of the tooth cuttingsurfaces is co-planar with an imaginary disc cutting plane.
 4. The bonecutter of claim 3 wherein the imaginary disc cutting plane is positionedbetween the first imaginary plane and the second imaginary plane.
 5. Thebone cutter of claim 1 wherein a second height of the second sidewallmeasured from a second sidewall proximal end to the second sidewalldistal end is greater than a first height of the first sidewall measuredfrom a first sidewall proximal end to the first sidewall distal end. 6.The bone cutter of claim 1 wherein a plurality of spaced apartconnectors are positioned radially between the inner surface of thefirst sidewall and the outer surface of the second sidewall to therebyconnect the first sidewall to the second sidewall.
 7. The bone cutter ofclaim 1 wherein a boss at the second sidewall proximal portion has athroughbore that is co-axial with the longitudinal axis.
 8. The honecutter of claim 1 wherein the cutter disc is composed of a biocompatiblemetal.
 9. The bone cutter of claim 1 wherein the outer annular disc edgecontacts an offset rim at the first inner surface of the first sidewall.10. The bone cutter of claim 1 wherein the cutter disc supported on thesecond sidewall distal end is removable therefrom for replacement of thecutter disc.
 11. A bone cutter, comprising: a) a first sidewallcomprising a first inner surface providing a first lumen extending alonga longitudinal axis from a first sidewall proximal portion to a firstsidewall distal portion having a first sidewall distal end residingalong a first imaginary plane; b) a second sidewall comprising a secondinner surface spaced from a second outer surface by a second thicknessto thereby provide a second lumen extending along the longitudinal axisfrom a second sidewall proximal portion to a second sidewall distalportion having a second sidewall distal end residing along a secondimaginary plane, c) wherein the first and second sidewalls are fixedlyjoined to each other in a co-axial relationship with the outer surfaceof the second sidewall being radially inside the inner surface of thefirst sidewall with the second imaginary plane being more proximal alongthe longitudinal, axis than the first imaginary plane to thereby providean offset; d) a cutter disc comprising a disc wall extending from anannular outer disc edge to an outer annular inner disc edge surroundinga disc opening, the cutter disc having a disc thickness extending from aproximal disc face to a planar distal disc face, wherein the proximalcutter disc face is supported on the second sidewall distal end with theannular outer disc edge contacting the inner surface of the firstsidewall distal portion; and e) a plurality of cutting teeth, eachcutting tooth having a tooth opening extending through the disc wall anda tooth cutting surface extending distally away from the planar distaldisc face and towards the first imaginary base plane, and wherein adistal end of each tooth cutting surface is co-planar with an imaginarydisc cutting plane fixedly positioned between the first and secondcylinder imaginary base planes, wherein each tooth opening provides opencommunication at least into the first lumen between the first and secondsidewalls.
 12. The bone cutter of claim 11 wherein an inner diameter ofthe second sidewall is greater than an inner diameter at the inner discedge of the cutter disc.
 13. The bone cutter of claim 11 wherein a bossat the second sidewall proximal portion has a throughbore that isco-axial with the longitudinal axis.
 14. The bone cutter of claim 11wherein a plurality of spaced apart connectors are positioned radiallybetween the inner surface of the first sidewall and the outer surface ofthe second sidewall to thereby connect the first sidewall to the secondsidewall.
 15. The bone cutter of claim 11 wherein the outer annular discedge contacts an offset rim at the first inner surface of the firstsidewall.
 16. The bone cutter of claim 11 wherein the cutter discsupported on the second sidewall distal end is removable therefrom forreplacement of the cutter disc.
 17. A bone cutter, comprising: a) afirst sidewall comprising a first inner surface providing a first lumenextending along a longitudinal axis from a first sidewall proximalportion to a first sidewall distal portion having a first sidewalldistal end residing along a first imaginary plane; b) a second sidewallcomprising a second inner surface spaced from a second outer surface bya second sidewall thickness to thereby provide a second lumen extendingalong the longitudinal axis from a second sidewall proximal portion to asecond sidewall distal portion having a second sidewall distal endresiding along a second imaginary plane, c) wherein the first and secondsidewalls are fixedly joined to each other in a co-axial relationship bya plurality of spaced apart connectors positioned radially between theinner surface of the first sidewall and the outer surface of the secondsidewall with the second imaginary plane being more proximal along thelongitudinal axis than the first imaginary plane to thereby provide anoffset; d) a boss at the second sidewall proximal portion having athroughbore that is co-axial with the longitudinal axis; e) a cutterdisc comprising a disc wall extending from an outer disc edge to aninner disc edge surrounding a disc opening, the cutter disc having adisc thickness extending from a proximal disc face to a distal discface, wherein the proximal cutter disc face is supported on the secondsidewall distal end with the annular outer disc edge in contact with theinner surface of the first sidewall distal portion; and f) a pluralityof cutting teeth on the cutter disc, each cutting tooth having a toothopening extending through the disc wall and a tooth cutting surfaceextending away from the distal disc face towards the first imaginaryplane, wherein the plurality of tooth cutting surfaces reside along athird imaginary plane that is between the first and second imaginaryplanes of the respective first and second sidewall distal ends, andwherein each tooth opening provides open communication into the firstand second lumens of the respective first and second sidewalls.
 18. Thebone cutter of claim 17 wherein an inner diameter of the second sidewallis greater than an inner diameter at the inner disc edge of the cutterdisc.